walk in the park vs piece of cake

Some examples from the web:

• My father is going for a walk in the park.
• A tastemaker as formidable as yourself, this should be a walk in the park.
• Go for a walk in the park.
• That morning, Dorrie and I had gone for a walk in the park.
• Walk in the park, right?
• It's just a walk in the park.
• The old man is taking a walk in the park.
• My father takes a walk in the park.
• Al Qaeda was a walk in the park.
• I could see him for a walk in the park.
• You missed a beautiful walk in the park.
• From where I stand, that makes social Darwinism look like a walk in the park.
• Welcome to the Year Ten Science Excursion which is quite literally a walk in the park - the Bremin Ranges National Park.
• After facing you live feeds and bloodthirsty journalists are a walk in the park.
• You give your dress to my wife and she goes for a walk in the park.
• Now those of you who have done this will realize that this is no walk in the park.
• Bill took a walk in the park to try and get some fresh air.
• That being said, dodging bullets and antitank missiles isn't exactly a walk in the park.
• I'd be willing to bet she's just composing herself, taking a nice, long, peaceful walk in the park.
• It looks more like you're going for a walk in the park, but...

Some examples from the web:

• Freeze time... piece of cake.
• A piece of cake, this detecting lark.
• Well, then your debrief should be a piece of cake.
• It's a piece of cake compared to all this promotion.
• Here, have a piece of cake.
• It's a piece of cake.
• Garden centre, piece of cake.
• Welding it was a piece of cake.
• This is a piece of cake for me.
• Come on, piece of cake.
• You said it would be a piece of cake.
• So you've lost your piece of cake.
• He could have you like a piece of cake.
• The piece of cake to go.
• This is a piece of cake.
• Should be a piece of cake.
• He was fed a piece of cake soaked with barbiturate.
• I saved you a piece of cake.
• Getting by that guy will be a piece of cake.
• You must save me a piece of cake.